As well known, in a shaft seal mechanism of a gas turbine, a steam turbine, a compressor, a waterwheel, a refrigerator, and a pump, a mechanism disclosed in PTL 1 is known as a shaft seal mechanism which seals a rotating shaft, in rotary machines.
FIG. 12 is a perspective view showing the schematic structure of a shaft seal mechanism 100 in the related art.
The shaft seal mechanism 100 includes shaft seal devices 102, which are housed in a housing 101 surrounding a rotating shaft R on a stator side.
The shaft seal device 102 includes a seal piece-laminated body 103 where a plurality of thin seal pieces 103a are laminated in the circumferential direction along the periphery of a rotating shaft R, a high-pressure side seal plate 104 that covers a part of the seal piece-laminated body 103 on a fluid high-pressure side in the axial direction, and a low-pressure side seal plate 105 that covers a part of the seal piece-laminated body 103 on a fluid low-pressure side in the axial direction. In the seal piece-laminated body 103, outer ends of the plurality of thin seal pieces 103a in the radial direction are connected to each other and inner ends of the plurality of thin seal pieces 103a in the radial direction are formed as free ends. Further, in the seal piece-laminated body 103, the outer ends of the thin seal pieces 103a are housed in the housing 101 and the respective thin seal pieces 103a are inclined in a tangential direction and extend from the housing 101 toward a rotating shaft R.
In the shaft seal mechanism 100 having the above configuration, when the rotating shaft R stops, the inner ends of the thin seal pieces 103a come into contact with the rotating shaft R with a predetermined pre-load. However, when the rotating shaft R is rotated, a floating force is applied to the thin seal pieces 103a by a dynamic pressure effect. A small gap is formed between the rotating shaft R and the thin seal pieces 103a by using this floating force, so that working fluid is sealed and the wear of the rotating shaft R and the respective thin seal pieces 103a is prevented.
Further, a gas pressure distribution in a small gap, which is formed at every two thin seal pieces adjacent to each other, is set by adjusting the dimensions of the high-pressure side seal plate and the low-pressure side seal plate in the radial direction. For example, if the low-pressure side seal plate is shorter than the high-pressure side seal plate, a gas pressure distribution in the small gap is set so that gas pressure is gradually reduced toward the outer end from the inner end. Furthermore, it is possible to make pressure act so as to aid the floating force that is generated by the dynamic pressure effect.